Check what it added up

See which numbers the computer has decided to add, and put it right when the guess is wrong.

When you press Add up, the program guesses which numbers you meant and draws a moving dotted line round them. It is usually right. The two seconds spent looking at that line is the difference between a total you can trust and one you cannot.

Key points

What to remember

Try this

Find a total in a spreadsheet you already have and press the box it sits in. Look at the wide bar along the top. If it reads =SUM(...), that total is looking after itself. If it reads a plain number, somebody typed it, and it stopped being true a while ago.

Practice: Check what it added up. Your first lesson is free, with no account or card; the rest are part of a Lantern plan. Interactive lessons require JavaScript.

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